Engine cowling



May 31, 1938 K. CAMPBELL v ENGINEKCOWLING Filed May 15, 1957 INVENTOR. irrmwwwmzzz Patented May 31, 1938 UNITED STATES PATENT OFFICE Wright Aeronautical tion of New York Corporation, a corpora- Application May 15, 1937, Serial No. 142,760

4 Claims.

This invention comprises improvements in annular anti-drag cowling adapted for use in connection with radial cylinder air-cooled engines.

In current types of aircraft, radial cylinder engines are mounted at the forward end of a streamlined body or nacelle structure, and for the purpose of reducing engine drag, and also for improving engine coo-ling, the engine is embraced by an annular cowling member provided with a forward air entrance opening and an air exit opening rearward of the engine and between the cowling and body. In normal practice, the air entrance opening is circular and concentric with the engine, and it has been found that under conditions of climb, where the engine axis is upwardly tilted with respect to the relative airstream, the cooling air entering the cowling has a tendency to recirculate and spill over the leading edge of the cowling to the detriment of effective engine cooling. It is an object of this invention to provide a very simple correction for the above indicated difficulty. It is a further object of the invention to provide in an engine embracing annular cowling, an air entrance opening of particular form whereby recirculation and spillage of air under high angle of attack conditions is minimized.

Further objects will be apparent from a reading of the subjoined specification and claims, and from an examination of the accompanying drawing, in which similar numbers indicate similar or like parts, and in which:

Fig. 1 is a front elevation of an annular cowling element embodying one form of the invention;

Fig. 2 is an axial section, through the cowling, showing its application to an aircraft power plant, and

Fig. 3 is a front elevation of an alternative form of the invention.

Fig. 2 shows the general organization of an annular engine embracing cowling Ill, suitably attached to a radial cylinder engine ll mounted, by structure II, to a body l3. The engine carrles at its forward end a propeller 14. The cowling comprises a main body portion l5 having a trailing edge I6 radially spaced from the body l3 to provide an annular air exit opening. The body l5 extends forwardly and blends into an inwardly curved leading edge portion l1 open at the front to provide an air entrance opening l8. Normally, such an opening 18 is circular and concentricwith the engine and tests have indicated that the diameter of this opening should be 65% to 80% of the engine diameter for good 55 drag reduction. Some installations have been built with the opening diameter approximately 85% of engine diameter in the interest of entraining a greater amount of cooling air within, the cowling. Such cowling installations are generally satisfactory in service, but it has been found that under steep climb conditions, where the engine axis is upwardly tilted with respect to the relative airstream, the top cylinders of the engine tend to run hot, indicating a loss of cooling air within the upper part of the cowling. This phenomenon is attributed to a spillage of cooling air from the top part of the air entrance opening. To correct this situation, I provide a bafiie or restriction l9 blanking off the top part of the air entrance opening I8, which, in Fig. 1, is shown as a segment integral with the leading edge portion ll of the cowling. In tests, this baffle l9 has proved effective in minimizing loss of cooling air from the top of the cowling, and has been found to have no adverse effect under low angle of attack, high speed flight conditions. Expressing the conformation of the cowl air entrance opening in another way, said opening comprises a segment of a circle whose are of embracement is of the order of 270, said are being symmetrical with respect to the plane of symmetry of the aircraft.

An alternative form of the invention is shown in Fig. 3, wherein the cowl air entrance opening I8 is in the form of a circle which is eccentric to the main part of the cowling and eccentric to the engine axis. In this instance, the center for the air entrance opening I8 is displaced directly below the engine axis whereby the cowl leading edge portion l'l' extends inwardly from the body portion IS a greater distance at the top of the cowling than at the bottom thereof. It is believed that such an ececntric air entrance opening would have substantially the same effect in reducing spillage of cooling air as the embodiment of Fig. 1.

In the application of either embodiment of the invention, the net area of the air entrance opening may readily be arranged to Provide for the entrainment of adequate cooling air under all ordinary flight conditions.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modiflcations and changes.

I claim as my invention:

1. An annular anti-drag cowling for embracement of a static air-cooled engine comprising a concentric iore-and-aft body portion, a concentric inturned leading edge portion defining an air entrance opening, and a segment portion covering the upper annular air entrance opening, whereby spillage of entering air is suppressed when the cowl axis is inclined to the direction of the attacking airstream, said cowling having an exit opening through which air entrained within the entrance opening may issue.

2. An annular anti-drag cowling for embracement of a static air-cooled engine comprising an inturned leading edge portion formed to define a forward air entrance opening, said opening being of substantially circular outline, the circle thereof being eccentric to and having its center below, the cowling axis, whereby spillage of entering air is suppressed when the cowl axis is inclined to the direction of the attacking airstream, said cowling having an exit opening through which air entrained within the entrance opening may issue.

3. In an aircraft power plant, a static radial cylinder engine, an annular cowling embracing the engine cylinders having a leading edge defining an air entrance opening ahead of the engine for the reception of cooling air, said cowling being subject to spillage of air toward the top of its leading edge when the cowl axis is inclined upwardly relative to the attacking airstream, and a bafiie across the uppermost segment of said opening for preventing said spillage, said cowling having an exit opening through which air entrained within the entrance opening may issue.

4. In aircraft an annular anti-drag cowling for embracement of an engine having a propeller shaft extending forwardly of and substantially concentric with the cowling, an inturned leading edge for said cowling defining a substantially central air entrance opening ahead of said engine including masking means forming an inward continuation of the uppermost part of said leading edge to restrict the effective area of the uppermost part of said air entrance opening, whereby spillage of air from within the cowling is suppressed during high angle of attack attitudes of the aircraft, said cowling having an exit opening through which air entrained within the entrance opening may issue.

KENNETH CAMPBELL. 

